The present invention relates generally to the undercarriage of a tracked vehicle. More particularly, it relates to a system for aligning undercarriage drive, idler and roller wheels of a work vehicle having a rubber track.
In the field of track systems for work vehicles, such as agricultural tractors and combines, a number of undercarriage arrangements have been proposed and are presently in use. Such undercarriages typically include a drive wheel and several idler and roller wheels arranged such that their rotational axes are parallel and the center planes of each wheel (i.e. a plane for a wheel that is perpendicular to that wheel""s rotational axis and passes through the center of the wheel) are coplanar. By arranging the wheels in this fashion, a track passing over the outside surface of the wheels is maintained in a fixed relationship with each wheel.
Providing and maintaining the alignment of the drive wheels with respect to the idler and roller wheels and the track is difficult due to manufacturing tolerances, uneven wear, and damage to suspension components. Typically, when the idler and roller wheels are misaligned with respect to the drive wheel, the track will not remain centered over each wheel as they rotate, but will migrate toward one side of the wheels over time. In the event the track is equipped with lugs (usually on its inner surface) to prevent such track migration, the migratory forces will force these lugs against the grooves in the wheels that receive the lugs and guide the track. This will cause the lugs to rapidly wear away.
To compensate for these factors, tracked vehicle undercarriage systems are usually adjustable, allowing relative motion between the drive wheels and other wheels of the undercarriage. U.S. Pat. No. 5,127,714 (the ""714 systemxe2x80x3) discloses one such system. In the ""714 system, a single drive wheel is provided at the after portion of the vehicle, a series of roller wheels extend forward of the drive wheel connected to a beam, and a forwardmost adjustable idler wheel is provided. The system disclosed in these patents allows the forwardmost idler wheel to be adjusted relative to the drive wheel. The idler wheel is mounted on a horizontally extending member that itself is adjustable with respect to the beam to which the roller wheels are attached. By pivoting the forwardly extending member inwardly or outwardly about pin 62, the center plane of the idler wheel may be moved in an axial direction. This pivoting is provided by alternatively loosening and tightening jack screws on both an inwardly facing and outwardly facing surface of the beam. Due to its position, the inwardly facing jack screw is difficult to adjust. While allowing the forwardmost idler wheel to be adjusted with respect to the drive wheel, this system does not apparently allow the roller wheels located between the drive wheel and the idler wheel to be adjusted. To adjust each of these wheels with respect to the drive wheel and the idler wheel would apparently require separate adjustment of each wheel.
In another device, shown in U.S. Pat. Nos. 5,312,176 and 5,293,948, the idler wheels 58 and 60 are similarly coupled to the forward end of the roller wheel frame, and are apparently adapted to pivot about pivot pins 102 and 104. These pins define a substantially vertical axis extending through the center of the idler wheel. A forked lever member 93 extends backward from the idler wheel and pivots the idler wheel about the pivot pins. Similar to the ""714 system, the idler wheel pivots when inward and outward facing screws 128 and 130 are adjusted. As with the ""714 system, the idler wheels do not adjust together with the idler wheel, nor is there a method for adjusting the idler wheels shown. They appear to be in a fixed relationship with respect to drive wheel 32. In a manner also similar to the ""714 system, adjustment of the idler wheel increases the tension on one side of the belt and reduces the tension on the other side of the belt, possibly accelerating wear and increasing the risk of failure. It is this increased tension that causes the track to be aligned, since an unequally tensioned track will migrate laterally across the idler toward the higher tensioned side as discussed below.
Neither of the above examples allow the idler and roller wheels to be collectively adjusted with respect to the drive wheel, thereby preserving their relative adjustment and allowing them to be collectively adjusted with respect to the drive wheel. Neither of the above examples maintains a constant track tension on either side of the elastomeric track, thus risking accelerated track wear.
There is a need, therefore, for an improved system for adjusting a tracked vehicle undercarriage. In particular, there is a need for an undercarriage that provides for easy adjustment. There is also a need for an undercarriage that can be adjusted without unequally tensioning the track. There is also a need for an adjustable undercarriage that preserves the alignment between the drive wheels and the idler wheels.
The present invention provides a novel apparatus for supporting and adjusting a tracked vehicle undercarriage that provides for the above needs.
Thus in accordance with the current invention, an undercarriage support and adjustment system for a tracked vehicle having a drive wheel is provided, including a first and second elongated outwardly extending members coupled to the vehicle, a first undercarriage bearing support coupled to the vehicle between said first and second outwardly extending members, and an undercarriage bearing support member slidingly coupled to the outer ends of the two support members and having a second undercarriage bearing support. The first member may extend outwardly forward of the drive wheel""s axis of rotation and the second member may extend outwardly in a position aft of the drive wheel""s axis of rotation. The first undercarriage bearing support may be coupled to the vehicle below the drive wheel""s axis and inside of the drive wheel, and the second undercarriage bearing support may be coupled to the vehicle below the drive wheels axis and outside of the drive wheel. The first and second undercarriage bearing supports may share a common axis that extends substantially laterally with respect to the vehicle. The undercarriage bearing support member may be coupled to the first and second members at first and second coupling points respectively, and the second undercarriage bearing support may be disposed between the first and second coupling points. The undercarriage bearing support member may have a plurality of elongate adjustment slots at the first and second coupling points. The first elongate member may have an adjusting screw and a fore-and-aft extending threaded boss for receiving the adjusting screw. The undercarriage bearing support member may have an abutting surface adapted to contact the end of the adjusting screw. The vehicle may also have an undercarriage with a plurality of wheels coupled to an elongate fore-and-aft wheel mounting beam with first and second laterally opposed mounting brackets coupled to the wheel mounting beam that are coupled to the first and second undercarriage bearing supports, respectively.
In accordance with a second embodiment of the invention, a method of aligning a tracked suspension includes the step of rotating a first wheel and track with respect to each other about a relative rotational axis that transects the wrap angle when the relative rotational axis is translated to intersect the first rotational axis. The relative rotational axis may be within 30 degrees (+/xe2x88x9230 degrees) of dividing the wrap angle into two equiangular portions, or may actually divide the wrap angle into two such portions. The rotation about the relative axis may be performed by rotating either track or wheel with respect to the other by rotating both together, or by rotating the track and at least one other wheel with respect to the first wheel.
Other principal features and advantages of the invention will become apparent to those skilled in the art upon review of the following drawings, the detailed description and the appended claims.